diff options
| author | Andy Lutomirski <luto@kernel.org> | 2015-09-20 16:32:05 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-22 14:49:18 -0700 |
| commit | c4cceeaf6604e8b7d71fe9729f78c73dbd4f79e4 (patch) | |
| tree | 77600e77f7877de56c36820b4bb5b833f3d1a794 /arch | |
| parent | 9cdde1d2df7ff6c1001c6d8b268ec39d0654355b (diff) | |
x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code
commit 83c133cf11fb0e68a51681447e372489f052d40e upstream.
The NMI entry code that switches to the normal kernel stack needs to
be very careful not to clobber any extra stack slots on the NMI
stack. The code is fine under the assumption that SWAPGS is just a
normal instruction, but that assumption isn't really true. Use
SWAPGS_UNSAFE_STACK instead.
This is part of a fix for some random crashes that Sasha saw.
Fixes: 9b6e6a8334d5 ("x86/nmi/64: Switch stacks on userspace NMI entry")
Reported-and-tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/974bc40edffdb5c2950a5c4977f821a446b76178.1442791737.git.luto@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index a95186d93368..d330840a2b18 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1281,9 +1281,12 @@ ENTRY(nmi) * we don't want to enable interrupts, because then we'll end * up in an awkward situation in which IRQs are on but NMIs * are off. + * + * We also must not push anything to the stack before switching + * stacks lest we corrupt the "NMI executing" variable. */ - SWAPGS + SWAPGS_UNSAFE_STACK cld movq %rsp, %rdx movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp |